Restoration of lateral hand grasp using natural sensors.

A closed-loop control system for controlling the key grip of a C6 tetraplegic patient was developed. Natural sensors served as the source of the feedback signal. The neural signals from cutaneous receptors were picked up by an implanted cuff electrode placed around the radial branch of the median nerve innervating the lateral part of the index finger. Mechanical stress applied to the skin, like pressure and slips, resulted in an increase in amplitude of the recorded neural signal. The goal of the study was to determine whether the recorded neural signals were able to indicate the slip of an object during lateral grasp and whether the slip could be stopped by increasing the grasp force through functional electrical stimulation of the thumb adductor and flexor.